Iran says it is ready for unconditional prisoner swap talks with the US because of fears that the coronavirus could put the lives of the prisoners at risk.
Iranian news website Khabaronline.ir quoted Cabinet spokesman Ali Rabiei as saying there is a "readiness for all prisoners" to be discussed without condition.
"But the US has refused to answer, so far," said Mr Rabiei.
"We hope that as the outbreak of the Covid-19 disease threatens the lives of Iranian citizens in the US prisons, the US government eventually will prefer lives to politics."
A senior US official said: "There has been no offer and no offer of direct talks."
Mr Rabiei said Iran considered the US government responsible for the health of the Iranian prisoners, adding that "it seems that the US has more readiness to bring the situation to an end".
Iranian media in recent months said there are several Iranians in US custody, including Sirous Asgari, a 60-year-old university professor.
Last week, US officials said they were making progress in efforts to secure the release of a detained Navy veteran in Iran. But they were also pushing back on Iranian suggestions that a swap was in the works for the imprisoned Iranian professor.
Ken Cuccinelli, the acting deputy Homeland Security secretary, said last week that the cases of American detainee Michael White in Iran and Mr Asgari had never been connected.
Mr White, from California, was detained in July 2018 while visiting a girlfriend in Iran. He was convicted of insulting Iran's supreme leader and posting private information online.
Mr White is among thousands of prisoners granted medical furloughs by Iran, one of the first countries to be hit hard by the coronavirus. But he has been forced to remain in the country.